The present invention relates generally to waste treatment and more particularly to methods and apparatus' for potentially infectious waste treatment which is operable at varying atmospheric pressures.
Often biohazardous materials or pests must be safely disposed of. For example, biohazardous materials exist at commercial or governmental waste disposal plants, on-site at hospitals, and other medical facilities. Additionally, infectious or potentially infectious waste and pests which threaten agriculture and ecological systems can enter U.S. borders from international flights, international ships, and international arrivals of private water crafts. These types of wastes are often referred to as quarantine wastes. Disposing of biohazardous and/or quarantine wastes and pests on-site can prevent expensive transportation costs and risks associated with such costs. On-site disposal can also be a powerful tool in the context of hazardous material intercepted at U.S. ports of entry. Fast and reliable disposal of infectious or potentially infectious material can mitigate or avoid catastrophic outbreaks.
When treating infectious waste for disposal, it is important to ensure that the ultimate waste product which is to be discarded is free from pathogenic microorganisms. It is also desirable, and in some instances required by law, to render the waste material in a condition such that individual components (e.g. disposable syringes, bandages, body fluid receptacles and body parts) are unrecognizable.
Potential waste disposal methods include incineration, autoclaving, microwaving or other non-incineration treatment methods with autoclaves and incineration being the most commonly used. Environmental regulations have severely limited the use of incineration for waste disposal, and alternative treatment methods (primarily steam autoclaving) are often used as an alternative. Typical problems associated with gravity and vacuum autoclaves include the requirement for large volume high pressure (>1 BAR) steam. These pressure vessels require initial and on-going certifications to ensure pressure vessel integrity; cooling towers to cool the autoclave at the end of the cycle; batch only (not continuous feed) systems. Treated waste material from the high pressure autoclaves is very wet and heavy causing increased disposal costs. Some of the available methods are not entirely effective at destroying pathogenic organisms. Some methods (e.g. autoclaving) are “batch” treatment systems which are inefficient in operation. Batch treatment systems limit treatment throughput and consequently require storage of untreated materials while the batch is “cooking”, creating additional needs for users. Most batch treatment methods require equipment which tends to be expensive to install and both expensive and labor intensive to operate. Further problems with current methods include foul odors, noxious gases, liquids, and solid particles which are exhausted to the atmosphere or discharged to sanitary sewage systems. For example, certain plastics when in the semi-solid state can release volatile organic compounds (VOC's) which are hazardous to the health and the environment.
Regulations require treatment temperatures of 212° F. for a specified period of time. Current steam sterilization systems designed to operate at atmospheric pressures are unable to operate at the correct temperatures when the system is located at differing elevations above sea level. In most thermodynamic processes the temperature of the system is directly proportional to the pressure of the system such that changes in the system pressure result in changes to the system temperature. For example, an atmospheric steam treatment system located at 5000 ft MSL operates in a relatively reduced pressure and correspondingly the operating temperature is reduced, in some cases below 212° F.
Thus, there is a need for continuous feed (not batch process) steam sterilization systems which are capable of operating at increased elevations while maintaining a gage pressure which is equivalent to or greater than atmospheric pressure at sea level in order to maintain a requisite system temperature of 212° F.